Hygroscopic actuating element



Jan. 19, 1937. 1. w. KNIGHT 2,068,415

HYGROSCOPIC ACTUATING ELEMENT Filed Dec. 7, 1955 a r" a J z I17 mentor Le/ W.- KNIGHT Patented Jan. 19, 1937 PATENT OFFICE HYGROSCOPIC ACTUATING ELEMENT Ira W. Knight, Providence, R. I., assignor to American Moistening Company, Providence,

R. I., a corporation of Maine Application December 7, 1935, Serial No. 53,440

3 Claims.

This invention relates to improvements in hygroscopic actuating elements. More especially it has to do with improving such an element made of animal membrane.

For some time past in devices and apparatus responsive to and actuated by changes in relative humidity, it has been established that a piece or strip of animal membrane is alertly responsive and surprisingly accurate over a considerable period of use. A convenient size of such a strip has been found to be about five or six inches long, approximately one inch Wide, and about 1/1000 of an inch thick. The ends of such a strip have been secured in suitable means intended to keep the strip flat and by which the tension on the strip might be transmitted thereto with substantial uniformity. It has developed, however, that such a fiat strip will in time begin to curl along its edges, the curl progressing from the secured ends toward the middle of the strip, where in some cases the width of the remaining flat surface may be reduced to only about a one-half inch in width. Obviously the entire surface of the curled or rolled-over portions is not so well exposed to the atmosphere, as that of the remaining flat portions. It has been found that the strip after its edges have curled over has changed its characteristics somewhat and an instrument using the skin needs a slight recalibration.

The object of the present invention is to prevent the curling over of the edges of the skin and insure the maintenance of the sensitivity and reliability of the element. Paradoxically as it may seem, the solution to the problem has been found in what amounts to very large increase in the amount of exposed edges. The improvement consists in cutting the original wide strip, after it has been assembled in the end fasteners, into a plurality of narrow strips. This is conveniently done by merely slitting the original strip from close by one fastener to close by the other.

The accompanying drawing shows the best mode in which I have contemplated applying the principles of my invention, but these are to be taken as merely illustrative and it is intended that the patent shall cover by suitable expression in the appended claims whatever features of patentable novelty exist in the invention disclosed.

In the drawing:

Figure l is a face view of a hygroscopic element prepared in accordance with my invention; and

Figure 2 is an edge view of the same.

Referring more particularly to the drawing, the element comprises a piece of animal membrane 1 having fastening means 2 at its ends which keep said ends fiat and enable the element to be attached to the device or apparatus actuated by the change in length of the membrane in accordance with changes of the humidity conditions of the atmosphere in which the element is exposed. A piece of fabric 3, preferably gummed cloth, is folded over each end edge of the membrane and a metallic stiffener 4, such as sheet copper, is similarly folded over the fabric. An eyelet 5 is riveted through the layers of metal and fabric to clamp them and the end of the strip securely together. Near the corners of the stiffeners 4, small indentations 6 of the metal may be made, if desired, by a prick punch.

The element as thus far described is what has been used and what has been found, after considerable use, to become curled inward along the edges e. I have found that such curling or rolling over of the edges, can be avoided by cutting the strip longitudinally intermediate of the fasteners. This is done most easily by merely slitting the strip as indicated by lines 5 in Figure 1. This results in a wide strip made up of a plurality of narrow strips Ia all integrally joined at their opposite ends.

Experience shows that with an element prepared as described above, the sensitivity and reliability continues accurate through many months of use (or of disuse) and are apparently permanent. This is most desirable in the art of humidification Where a hygroscopic element which is alertly responsive to humidity changes and reliably maintains its characteristics is of very great importance.

I claim:

1. A hygroscopic actuating element comprising a piece of hygroscopically responsive animal membrane having slits extending longitudinally thereof intermediately of its ends.

2. A hygroscopic actuating element comprising a piece of hygroscopically responsive animal membrane having longitudinally disposed slits intermediately of its ends forming a series of strips extending longitudinally thereof and integrally joined at their ends.

3. A hygroscopic actuating element comprising a piece of hygroscopically responsive animal membrane having means at its ends for applying tension thereto, a series of slits extending intermediately of said means in the direction of pull and dividing the piece of membrane into separate strips integrally connected in the region of said means.

IRA W. KNIGHT. 

